I was born and brought up in the country and spent much time in my childhood and youth helping parents and grandparents to look after their extensive fruit and vegetable gardens. Like you, we avoided mechanical aids and the gardens supplied virtually all our fruit and vegetables. There was food rationing just after the war, and so such gardens were vital for the food supply. (Even now, my family in the UK live in the country, breed horses and run a large farm.)

But there was no hint of romanticism about the close relation with Mother Nature. Though he was a lot older than me, I suspect that Kisshomaru had a similar experience in Iwama, probably more acute, since Japan's economic situation was much worse than the UK's.

So it might be that O Sensei really believed that aikido was close to farming. But he was using a trope, which was based on a much more romantic view of the relationship.